Sudoku is a puzzle game, where the object is to use the numbers from 1-9 to fill every row, column and box. Each number can only occur once in every row, column or box. A number of fields will have numbers in them at the start, the rest will be filled in by you. If you manage to fill all the fields without ever having a duplicate number in a unit (row, column or box), you win the game.
There are a number of complicated strategies you can use to figure out the right numbers. The most basic one is of course to just look at a single row, column or unit and see if there is any field where there's only one possibility. Each field is a part of one row, one column and one box. So, if you're looking at a field and see that in its row you have 1,2,3, in its column you have 4,5,6 and in its box you have 7,8, then you know that only 9 can fit in that box, since any other number would create duplicates in one of its units.
Of course there are also many other strategies to use, but we won't go into them here. Couple of useful things to know:
You can always print the puzzle currently on screen, doesn't matter if it's partially filled in, just hit the Print button in your browser and you'll get a clean printout of only the puzzle without anything filled in, and without any of the extra webpage text. Just try it!
Sudoku.lol is made by the CardGames.io team. We already have a Sudoku game on our main site but figured it would be nice to have a special site only for Sudoku. If you're on a phone we highly recommend adding a shortcut to the game to your homescreen, that will let you start up in full screen mode, and will feel almost exactly like an app.
This is version 51 of Sudoku.lol